The invention relates in general to sound attenuation and, more specifically, to mufflers for use with internal combustion engines to reduce exhaust gas sound therefrom.
In many devices such as internal combustion engines, turbine engines, compressed gas powered tools, air handling systems, etc., considerable noise energy is generated and travels with the fluid or gasses. Such noise is objectionable and must be reduced prior to exit from a noisy device. A wide variety of "mufflers" and other sound attenuation devices have been developed and used.
Some mufflers use a plurality of baffles which radically change the path of the exhaust gas over a short distance. While such mufflers may be effective in reducing noise levels, they create undesirable high back pressure on the engines and reduce the column inertia of the exhaust gas flow, resulting in lower engine power and efficiency.
Other mufflers direct gasses straight through a perforated tube surrounded by sound absorbing material such as, glass fibers in the form of "glass wool" positioned between the tube and outer housing. These so called "glass-pack" mufflers generally produce low back pressure, are not satisfactory in reducing noise levels and lack long term durability.
Generally speaking, prior art mufflers have flow through resistance, produce acoustic wave reflection and cause a loss of column inertia.
Many attempts have been made to produce the ideal muffler. Some of these attempts can be found in the following U.S. Pat. Nos. 1,934,462; 1,922,848; 2,046,193; 2,826,261; 4,239,091; 4,632,216; 4,671,381; 4,674,594 and 4,690,245 and others. None of these prior art mufflers have reached an ultimate of sufficient reducing sound while maintaining column inertia with minimum flow loss.
Also some of these prior art mufflers are complex to manufacture, heavy in weight and overly large for the purpose intended and others have a short life due to corrosion or are susceptible to burn out from the heat of the gasses passing therethrough.
Applicant's prior U.S. Pat. Nos. 4,263,982 and 4,834,214 have considerably advanced the muffler art.
There is, however, a continuing need to further improve the sound attenuation to further reduce noise pollution. The muffler of the present invention advances the current state of the muffler art in this area of desired improvement.